I have just started using commands and command blocks, and my iPad has started to freeze constantly while on the app, between 10 and 20 seconds each freeze. I believe that it is due to the use of them, as it hasn't happened before. A friend of mine is having the exact same problem – with the exact same device, software, and version of Minecraft. We have tried deleting worlds to make more space, and hopefully to stop the freezing, but it has been to no avail.